Method for Reducing Acrylamide Formation in Thermally Processed Foods

ABSTRACT

In fabricated, thermally processed snack foods, the addition of one of a select group of amino acids to the recipe for the food inhibits the formation of acrylamide during the thermal processing. The amino acid can come from the group of cysteine, lysine, glycine, histidine, alanine, methionine, glutamic acid, aspartic acid, proline, phenylalanine, valine, and arginine and can be a commercially available amino acid or in a free form in an ingredient added to the food. Amino acids can be added to fabricated foods at the admix stage or by exposing raw food stock to a solution containing a concentration of the amino acid additive.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a method for reducing the amount ofacrylamide in thermally processed foods. This invention permits theproduction of foods having significantly reduced levels of acrylamide.The method relies on the use of one or more of a select group of aminoacids in the manufacture of a snack food.

2. Description of Related Art

The chemical acrylamide has long been used in its polymer form inindustrial applications for water treatment, enhanced oil recovery,papermaking, flocculants, thickeners, ore processing and permanent pressfabrics. Acrylamide participates as a white crystalline solid, isodorless, and is highly soluble in water (2155 g/L at 30° C.). Synonymsfor acrylamide include 2-propenamide, ethylene carboxamide, acrylic acidamide, vinyl amide, and propenoic acid amide. Acrylamide has a molecularmass of 71.08, a melting point of 84.5° C., and a boiling point of 125°C. at 25 mmHg.

In very recent times, a wide variety of foods have tested positive forthe presence of acrylamide monomer. Acrylamide has especially been foundprimarily in carbohydrate food products that have been heated orprocessed at high temperatures. Examples of foods that have testedpositive for acrylamide include coffee, cereals, cookies, potato chips,crackers, french-fried potatoes, breads and rolls, and fried breadedmeats. In general, relatively low contents of acrylamide have been foundin heated protein-rich foods, while relatively high contents ofacrylamide have been found in carbohydrate-rich foods, compared tonon-detectable levels in unheated and boiled foods. Reported levels ofacrylamide found in various similarly processed foods include a range of330-2,300 (μg/kg) in potato chips, a range of 300-1100 (μg/kg) in frenchfries, a range 120-180 (μg/kg) in corn chips, and levels ranging fromnot detectable up to 1400 (μg/kg) in various breakfast cereals.

It is presently believed that acrylamide is formed from the presence ofamino acids and reducing sugars. For example, it is believed that areaction between free asparagine, an amino acid commonly found in rawvegetables, and free reducing sugars accounts for the majority ofacrylamide found in fried food products. Asparagine accounts forapproximately 40% of the total free amino acids found in raw potatoes,approximately 18% of the total free amino acids found in high proteinrye, and approximately 14% of the total free amino acids found in wheat.

The formation of acrylamide from amino acids other than asparagine ispossible, but it has not yet been confirmed to any degree of certainty.For example, some acrylamidc formation has been reported from testingglutamine, methionine, cysteine, and aspartic acid as precursors. Thesefindings are difficult to confirm, however, due to potential asparagineimpurities in stock amino acids. Nonetheless, asparagine has beenidentified as the amino acid precursor most responsible for theformation of acrylamide.

Since acrylamide in foods is a recently discovered phenomenon, its exactmechanism of formation has not been confirmed. However, it is nowbelieved that the most likely route for acrylamide formation involves aMaillard reaction. The Maillard reaction has long been recognized infood chemistry as one of the most important chemical reactions in foodprocessing and can affect flavor, color, and the nutritional value ofthe food. The Maillard reaction requires heat, moisture, reducingsugars, and amino acids.

The Maillard reaction involves a series of complex reactions withnumerous intermediates, but can be generally described as involvingthree steps. The first step of the Maillard reaction involves thecombination of a free amino group (from free amino acids and/orproteins) with a reducing sugar (such as glucose) to form Amadori orHeyns rearrangement products. The second step involves degradation ofthe Amadori or Heyns rearrangement products via different alternativeroutes involving deoxyosones, fission, or Strecker degradation. Acomplex series of reactions—including dehydration, elimination,cyclization, fission, and fragmentation—results in a pool of flavorintermediates and flavor compounds. The third step of the Maillardreaction is characterized by the formation of brown nitrogenous polymersand co-polymers. Using the Maillard reaction as the likely route for theformation of acrylamide, FIG. 1 illustrates a simplification ofsuspected pathways for the formation of acrylamide starting withasparagine and glucose.

Acrylamide has not been determined to be detrimental to humans, but itspresence in food products, especially at elevated levels, isundesirable. As noted previously, relatively higher concentrations ofacrylamide are found in food products that have been heated or thermallyprocessed. The reduction of acrylamide in such food products could beaccomplished by reducing or eliminating the precursor compounds thatform acrylamide, inhibiting the formation of acrylamide during theprocessing of the food, breaking down or reacting the acrylamide monomeronce formed in the food, or removing acrylamide from the product priorto consumption. Understandably, each food product presents uniquechallenges for accomplishing any of the above options. For example,foods that are sliced and cooked as coherent pieces may not be readilymixed with various additives without physically destroying the cellstructures that give the food products their unique characteristics uponcooking. Other processing requirements for specific food products maylikewise make acrylamide reduction strategies incompatible or extremelydifficult.

By way of example, FIG. 2 illustrates well-known prior art methods formaking fried potato chips from raw potato stock. The raw potatoes, whichcontain about 80% or more water by weight, first proceed to a peelingstep 21. After the skins are peeled from the raw potatoes, the potatoesare then transported to a slicing step 22. The thickness of each potatoslice at the slicing step 22 is dependent on the desired the thicknessof the final product. An example in the prior art involves slicing thepotatoes to about 0.053 inches in thickness. These slices arc thentransported to a washing step 23, wherein the surface starch on eachslice is removed with water. The washed potato slices are thentransported to a cooking step 24. This cooking step 24 typicallyinvolves frying the slices in a continuous fryer at, for example, 177°C. for approximately 2.5 minutes. The cooking step generally reduces themoisture level of the chip to less than 2% by weight. For example, atypical fried potato chip exits the fryer at approximately 1.4% moistureby weight. The cooked potato chips are then transported to a seasoningstep 25, where seasonings are applied in a rotation drum. Finally, theseasoned chips proceed to a packaging step 26. This packaging step 26usually involves feeding the seasoned chips to one or more weighers thatthen direct chips to one or more vertical form, fill, and seal machinesfor packaging in a flexible package. Once packaged, the product goesinto distribution and is purchased by a consumer.

Minor adjustments in a number of the potato chip processing stepsdescribed above can result in significant changes in the characteristicsof the final product. For example, an extended residence time of theslices in water at the washing step 23 can result in leaching compoundsfrom the slices that provide the end product with its potato flavor,color and texture. Increased residence times or heating temperatures atthe cooking step 24 can result in an increase in the Maillard browninglevels in the chip, as well as a lower moisture content. If it isdesirable to incorporate ingredients into the potato slices prior tofrying, it may be necessary to establish mechanisms that provide for theabsorption of the added ingredients into the interior portions of theslices without disrupting the cellular structure of the chip or leachingbeneficial compounds from the slice.

By way of another example of heated food products that represent uniquechallenges to reducing acrylamide levels in the final products, snackscan also be made from a dough. The term “fabricated snack” means a snackfood that uses as its starting ingredient something other than theoriginal and unaltered starchy starting material. For example,fabricated snacks include fabricated potato chips that use a dehydratedpotato product as a starting material and corn chips that use a masaflour as its starting material. It is noted here that the dehydratedpotato product can be potato flour, potato flakes, potato granules, orany other form in which dehydrated potatoes exist. When any of theseterms are used in this application, it is understood that all of thesevariations are included.

Referring back to FIG. 2, a fabricated potato chip does not require thepeeling step 21, the slicing step 22, or the washing step 23. Instead,fabricated potato chips start with, for example, potato flakes, whichare mixed with water and other minor ingredients to form a dough. Thisdough is then sheeted and cut before proceeding to a cooking step. Thecooking step may involve frying or baking. The chips then proceed to aseasoning step and a packaging step. The mixing of the potato doughgenerally lends itself to the easy addition of other ingredients.Conversely, the addition of such ingredients to a raw food product, suchas potato slices, requires that a mechanism be found to allow for thepenetration of ingredients into the cellular structure of the product.However, the addition of any ingredients in the mixing step must be donewith the consideration that the ingredients may adversely affect thesheeting characteristics of the dough as well as the final chipcharacteristics.

It would be desirable to develop one or more methods of reducing thelevel of acrylamide in the end product of heated or thermally processedfoods. Ideally, such a process should substantially reduce or eliminatethe acrylamide in the end product without adversely affecting thequality and characteristics of the end product. Further, the methodshould be easy to implement and, preferably, add little or no cost tothe overall process.

SUMMARY OF THE INVENTION

In the inventive process, one or more selected amino acids are added tofoods prior to cooking to reduce the formation of acrylamide. The aminoacid(s) can be added during milling, dry mix, wet mix, or other admix,so that the amino acid is present throughout the food product. The aminoacid can also be incorporated into raw foods by exposing the raw foodingredient to the amino acid, such as by soaking. The amino acid can bein the form of either a commercially available chemical or a foodproduct in which the amino acid is present in a free form. The additionof cysteine or lysine has been shown to reduce acrylamide formation intwo embodiments of the invention. Selected other amino acids have alsobeen shown to reduce acrylamide formation.

The addition of one or more selected amino acids effectively reduces theamount of acrylamide found in the end product of the heated or thermallyprocessed food while minimally affecting the quality and characteristicsof the end product. Further, such a method of acrylamide reduction isgenerally easy to implement and adds little or no cost to the overallprocess.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the invention are setforth in the appended claims. The invention itself, however, as well asa preferred mode of use, further objectives and advantages thereof, willbe best understood by reference to the following detailed description ofillustrative embodiments when read in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is a schematic of suspected chemical pathways for acrylamideformation in foods;

FIG. 2 is a schematic of prior art potato chip processing steps;

FIG. 3 is a schematic of a method for making fabricated potato chipsfrom potato flakes, granules or flour according to an embodiment of thepresent invention; and

FIG. 4 is a graph representation of the effects of the addition ofcysteine and lysine to fabricated potato chips.

DETAILED DESCRIPTION Effect of Amino Acids on Acrylamide Formation

The formation of acrylamide in thermally processed foods requires asource of carbon and a source of nitrogen. It is hypothesized thatcarbon is provided by a carbohydrate source and nitrogen is provided bya protein source or amino acid source. Many plant-derived foodingredients such as rice, wheat, corn, barley, soy, potato and oatscontain asparagine and are primarily carbohydrates having minor aminoacid components. Typically, such food ingredients have a small aminoacid pool, which contains other amino acids in addition to asparagine.

By “thermally processed” is meant food or food ingredients whereincomponents of the food, such as a mixture of food ingredients, areheated at temperatures of at least 80° C. Preferably the thermalprocessing of the food or food ingredients takes place at temperaturesbetween about 100° C. and 205° C. The food ingredient may be separatelyprocessed at elevated temperature prior to the formation of the finalfood product. An example of a thermally processed food ingredient ispotato flakes, which is formed from raw potatoes in a process thatexposes the potato to temperatures as high as 170° C. (The terms “potatoflakes”, “potato granules”, and “potato flour” are used interchangeablyherein, and are meant to denote any potato based, dehydrated product.)Examples of other thermally processed food ingredients include processedoats, par-boiled and dried rice, cooked soy products, corn masa, roastedcoffee beans and roasted cacao beans. Alternatively, raw foodingredients can be used in the preparation of the final food productwherein the production of the final food product includes a thermalheating step. One example of raw material processing wherein the finalfood product results from a thermal heating step is the manufacture ofpotato chips from raw potato slices by the step of frying at atemperature of from about 100° C. to about 205° C. or the production offrench fries fried at similar temperatures.

In accordance with the present invention, however, a significantformation of acrylamide has been found to occur when the amino acidasparagine is heated in the presence of a reducing sugar. Heating otheramino acids such as lysine and alanine in the presence of a reducingsugar such as glucose does not lead to the formation of acrylamide. But,surprisingly, the addition of other amino acids to the asparagine-sugarmixture can increase or decrease the amount of acrylamide formed.

Having established the rapid formation of acrylamide when asparagine isheated in the presence of a reducing sugar, a reduction of acrylamide inthermally processed foods can be achieved by inactivating theasparagine. By “inactivating” is meant removing asparagine from the foodor rendering asparagine non-reactive along the acrylamide formationroute by means of conversion or binding to another chemical thatinterferes with the formation of acrylamide from asparagine.

I: Effect of Cysteine, Lysine, Glutamine and Glycine on AcrylamideFormation

Since asparagine reacts with glucose to form acrylamide, increasing theconcentration of other free amino acids may affect the reaction betweenasparagine with glucose and reduce acrylamidc formation. For thisexperiment, a solution of asparagine (0.176%) and glucose (0.4%) wasprepared in pH 7.0 sodium phosphate buffer. Four other amino acids,glycine (GLY), lysine (LYS), glutamine (GLN), and cysteine (CYS) wereadded at the same concentration as glucose on a molar basis. Theexperimental design was full factorial without replication so allpossible combinations of added amino acids were tested. The solutionswere heated at 120° C. for 40 minutes before measuring acrylamide. Table1 below shows the concentrations and the results. TABLE 1 Glucose ASNGLY LYS GLN CYS acrylamide Order % % % % % % ppb 1 0.4 0.176 0 0 0 01679 2 0.4 0.176 0 0 0 0.269 4 3 0.4 0.176 0 0 0.324 0 5378 4 0.4 0.1760 0 0.324 0.269 7 5 0.4 0.176 0 0.325 0 0 170 6 0.4 0.176 0 0.325 00.269 7 7 0.4 0.176 0 0.325 0.324 0 1517 8 0.4 0.176 0 0.325 0.324 0.2697 9 0.4 0.176 0.167 0 0 0 213 10 0.4 0.176 0.167 0 0 0.269 6 11 0.40.176 0.167 0 0.324 0 2033 12 0.4 0.176 0.167 0 0.324 0.269 4 13 0.40.176 0.167 0.325 0 0 161 14 0.4 0.176 0.167 0.325 0 0.269 4 15 0.40.176 0.167 0.325 0.324 0 127 16 0.4 0.176 0.167 0.325 0.324 0.269 26

As shown in the table above, glucose and asparagine without any otheramino acid formed 1679 ppb acrylamide. The added amino acids had threetypes of effects.

1) Cysteine almost eliminated acrylamide formation. All treatments withcysteine had less than 25 ppb acrylamide (a 98% reduction).

2) Lysine and glycine reduced acrylamide formation but not as much ascysteine. All treatments with lysine and/or glycine but withoutglutamine and cysteine had less than 220 ppb acrylamide (a 85%reduction).

3) Surprisingly, glutamine increased acrylamide formation to 5378 ppb(200% increase). Glutamine plus cysteine did not form acrylamide.Addition of glycine and lysine to glutamine reduced acrylamideformation.

These tests demonstrate the effectiveness of cysteine, lysine, andglycine in reducing acrylamide formation. However, the glutamine resultsdemonstrate that not all amino acids are effective at reducingacrylamide formation. The combination of cysteine, lysine, or glycinewith an amino acid that alone can accelerate the formation of acrylamide(such as glutamine) can likewise reduce the acrylamide formation.

II. Effect of Cysteine, Lysine, Glutamine, and Methionine at DifferentConcentrations and Temperatures

As reported above, cysteine and lysine reduced acrylamide when added atthe same concentration as glucose. A follow up experiment was designedto answer the following questions:

-   -   1) How do lower concentrations of cysteine, lysine, glutamine,        and methionine effect acrylamide formation?    -   2) Are the effects of added cysteine and lysine the same when        the solution is heated at 120° C. and 150° C.?

A solution of asparagine (0.176%) and glucose (0.4%) was prepared in pH7.0 sodium phosphate buffer. Two concentrations of amino acid (cysteine(CYS), lysine (LYS), glutamine (GLN), or methionine (MET)) were added.The two concentrations were 0.2 and 1.0 moles of amino acid per mole ofglucose. In half of the tests, two ml of the solutions were heated at120° C. for 40 minutes; in the other half, two ml were heated at 150° C.for 15 minutes. After heating, acrylamide was measured by GC-MS, withthe results shown in Table 2. The control was asparagine and glucosesolution without an added amino acid. TABLE 2 Acrylamide level AminoPercent- Amino Amino acid/ Acid @ age Of Acid @ Percentage TemperatureControl Conc. 0.2 Control Conc. 1.0 Of Control LYS-120° C. 1332 ppb 1109ppb 83%  280 ppb 21% CYS-120° C. 1332 ppb  316 ppb 24%  34 ppb 3%LYS-150° C. 3127 ppb 1683 ppb 54%  536 ppb 17% CYS-150° C. 3127 ppb 1146ppb 37%  351 ppb 11% GLN-120° C. 1953 ppb 4126 ppb 211% 6795 ppb 348%MET-120° C. 1953 ppb 1978 ppb 101% 1132 ppb 58% GLN-150° C. 3866 ppb7223 ppb 187% 9516 ppb 246% MET-150° C. 3866 ppb 3885 ppb 100% 3024 ppb78%

In the tests with cysteine and lysine, a control formed 1332 ppb ofacrylamide after 40 minutes at 120° C., and 3127 ppb of acrylamide after15 minutes at 150° C. Cysteine and lysine reduced acrylamide formationat 120° C. and 150° C., with the acrylamide reduction being roughlyproportional to the concentration of added cysteine or lysine.

In the tests with glutamine and methionine, a control formed 1953 ppb ofacrylamide after 40 minutes at 120° C. and a control formed 3866 ppb ofacrylamide after 15 minutes at 150° C. Glutamine increased acrylamideformation at 120° C. and 150° C. Methionine at 0.2 mole/mole of glucosedid not affect acrylamide formation. Methionine at 1.0 mole/mole ofglucose reduced acrylamide formation by less than fifty percent.

III. Effect of Nineteen Amino Acids on Acrylamide Formation in Glucoseand Asparagine Solution

The effect of four amino acids (lysine, cysteine, methionine, andglutamine) on acrylamide formation was described above. Fifteenadditional amino acids were tested. A solution of asparagine (0.176%)and glucose (0.4%) was prepared in pH 7.0 sodium phosphate buffer. Thefifteen amino acids were added at the same concentration as glucose on amolar basis. The control contained asparagine and glucose solutionwithout any other amino acid. The solutions were heated at 120° C. for40 minutes before measuring acrylamide by GC-MS. The results are givenin Table 3 below. TABLE 3 Acrylamide Formed Amino Acid ppb % of ControlControl 959 100 Histidine 215 22 Alanine 478 50 Methionine 517 54Glutamic Acid 517 54 Aspartic Acid 529 55 Proline 647 67 Phenylalanine648 68 Valine 691 72 Arginine 752 78 Tryptophan 1059 111 Threonine 1064111 Tyrosine 1091 114 Leucine 1256 131 Serine 1296 135 Isoleucine 1441150

As seen in the table above, none of the fifteen additional amino acidswere as effective as cysteine, lysine, or glycine in reducing acrylamideformation. Nine of the additional amino acids reduced acrylamide to alevel between 22-78% of control, while six amino acids increasedacrylamide to a level between 111-150% of control.

Table 4 below summarizes the results for all amino acids, listing theamino acids in the order of their effectiveness. Cysteine, lysine, andglycine were effective inhibitors, with the amount of acrylamide formedless than 15% of that formed in the control. The next nine amino acidswere less effective inhibitors, having a total acrylamide formationbetween 22-78% of that formed in the control. The next seven amino acidsincreased acrylamide. Glutamine caused the largest increase ofacrylamide, showing 320% of control. TABLE 4 Acrylamide produced AminoAcid as % of Control Control 100% Cysteine 0% Lysine 10% Glycine 13%Histidine 22% Alanine 50% Methionine 54% Glutamic Acid 54% Aspartic Acid55% Proline 67% Phenylalanine 68% Valine 72% Arginine 78% Tryptophan111% Threonine 111% Tyrosine 114% Leucine 131% Serine 135% Isoleucine150% Glutamine 320%IV: Potato Flakes with 750 ppm of Added L-Cysteine

Test potato flakes were manufactured with 750 ppm (parts per million) ofadded L-cysteine. The control potato flakes did not contain addedL-cysteine. Three grams of potato flakes were weighed into a glass vial.After tightly capping, the vials were heated for 15 minutes or 40minutes at 120° C. Acrylamide was measured by GC-MS in parts per billion(ppb). TABLE 5 Acrylamide (ppb) Acrylamide Acrylamide Potato 15 Min atReduction Acrylamide (ppb) Reduction Flakes 120° C. 15 Min 40 Min at120° C. 40 Min Control 1662 — 9465 — 750 ppm 653 60% 7529 20% CysteineV. Baked Fabricated Potato Chips

Given the above results, preferred embodiments of the invention havebeen developed in which cysteine or lysine was added to the formula fora fabricated snack food, in this case baked, fabricated potato chips.The process for making this product is shown in FIG. 3. In a doughpreparation step 31, potato flakes, water, and other ingredients arecombined to form a dough. (The terms “potato flakes” and “potato flour”are used interchangeably herein and either are intended to encompass alldried flake or powder preparations, regardless of particle size.) In asheeting step 32, the dough is run through a sheeter, which flattens thedough, and is then cut into discrete pieces. In a cooking step 33, thecut pieces are baked until they reach a specified color and watercontent. The resulting chips are then seasoned in a seasoning step 34and placed in packages in a packaging step 35.

A first embodiment of the invention is demonstrated by use of theprocess described above. To illustrate this embodiment, a comparison ismade between a control and test batches to which were added either oneof three concentrations of cysteine or one concentration of lysine.Table 6 below shows the ingredients used in the various batches. TABLE 6Cysteine Cysteine Cysteine Ingredient Control #1 #2 #3 Lysine Potatoflakes and modified starch 5496 g 5496 g 5496 g 5496 g 5496 g Sugar 300g 300 g 300 g 300 g 300 g Oil 90 g 90 g 90 g 90 g 90 g Leavening agents54 g 54 g 54 g 54 g 54 g Emulsifier 60 g 60 g 60 g 60 g 60 g L-Cysteinc(dissolved in water)¹ 0 g 1.8 g 4.2 g 8.4 g 0 g L-Lysinemonohydrochloride 0 g 0 g 0 g 0 g 42 g Total Dry 6000 g 6001.8 g 6004.2g 6008.4 g 6042 g Water 3947 ml 3947 ml 3947 ml 3947 ml 3947 ml¹It is expected that the D-isomer or a racemic mixture of both the D-and L-isomers of the amino acids would be equally effective, althoughthe L-isomer is likely to be the best and least expensive source.

In all batches, the dry ingredients were first mixed together, then oilwas added to each dry blend and mixed. The cysteine or lysine wasdissolved in the water prior to adding to the dough. The moisture levelof the dough prior to sheeting was 40% to 45% by weight. The dough wassheeted to produce a thickness of between 0.020 and 0.030 inches, cutinto chip-sized pieces, and baked.

After cooking, testing was performed for moisture, oil, and coloraccording to the Hunter L-A-B scale. Samples were tested to obtainacrylamide levels in the finished product. Table 7 below shows theresults of these analyses. TABLE 7 Cysteine Cysteine CysteineMeasurement Control #1 #2 #3 Lysine H₂O 2.21% 1.73% 2.28% 2.57% 2.68%Oil, % 1.99% 2.15% 2.05% 2.12% 1.94% Acrylamide 1030 ppb 620 ppb 166 ppb104 ppb 456 ppb Color L 72.34 76.53 79.02 78.36 73.2 A 1.99 −1.14 −2.02−2.14 1.94 B 20.31 25.52 23.2 23.0 25.77

In the control chips, the acrylamide level after final cooking was 1030ppb. Both the addition of cysteine, at all the levels tested, and lysinereduced the final acrylamide level significantly. FIG. 4 shows theresulting acrylamide levels in graphical form.

Adding cysteine or lysine to the dough significantly lowers the level ofacrylamide present in the finished product. The cysteine samples showthat the level of acrylamide is lowered in roughly a direct proportionto the amount of cysteine added. Consideration must be made, however,for the collateral effects on the characteristics (such as color, taste,and texture) of the final product from the addition of an amino acid tothe manufacturing process.

Additional tests were also run, using added cysteine, lysine, andcombinations of each of the two amino acids with CaCl₂. These tests usedthe same procedure as described in the tests above, but used potatoflakes having varying levels of reducing sugars and varying amounts ofamino acids and CaCl₂ added. In Table 8 below, lot 1 of potato flakeshad 0.81% reducing sugars (this portion of the table reproduces theresults from the test shown above), lot 2 had 1.0% and lot 3 had 1.8%reducing sugars. TABLE 8 CaCl2 Cysteine Lysine Finish Finish Flake Wt %of ppm of % of H2O color Acrylamide Lot # total dry total dry total drywt % value ppb 1 0 0 0 2.21 72.34 1030 1 0 300 0 1.73 76.53 620 1 0 7000 2.28 79.02 166 1 0 1398 0 2.57 78.36 104 1 0 0 0.685 2.68 73.20 456 20 0 0 1.71 72.68 599 2 0 0 0 1.63 74.44 1880 2 0 0 0 1.69 71.26 1640 2 00 0 1.99 71.37 1020 2 0 700 0 2.05 75.81 317 2 0.646 0 0.685 1.74 73.99179 3 0 0 0 1.80 73.35 464 3 0 0 0 1.61 72.12 1060 3 0 700 0 1.99 75.27290 3 0 1398 0 1.96 75.87 188 3 0 0 0.685 1.90 76.17 105 3 0.646 0 0.6852.14 75.87 47 3 0.646 700 0 1.83 77.23 148

As shown by the data in this table, the addition of either cysteine orlysine provides significant improvement in the level of acrylamide ateach level of reducing sugars tested. The combination of lysine withcalcium chloride provided an almost total elimination of acrylamideproduced, despite the fact that this test was run with the highest levelof reducing sugars.

VI. Tests in Sliced, Fried Potato Chips

A similar result can be achieved with potato chips made from potatoslices. However, the desired amino acid cannot be simply mixed with thepotato slices, as with the embodiments illustrated above, since thiswould destroy the integrity of the slices. In one embodiment, the potatoslices are immersed in an aqueous solution containing the desired aminoacid additive for a period of time sufficient to allow the amino acid tomigrate into the cellular structure of the potato slices. This can bedone, for example, during the washing step 23 illustrated in FIG. 2.

Table 9 below shows the result of adding one weight percent of cysteineto the wash treatment that was described in step 23 of FIG. 2 above. Allwashes were at room temperature for the time indicated; the controltreatments had nothing added to the water. The chips were fried incottonseed oil at 178° C. for the indicated time. TABLE 9 Fry TimeFinished Finished Finished (seconds) H₂O wt % oil wt % AcrylamideControl - 2-3 min 140 1.32% 42.75% 323 ppb wash 1% cysteine - 15 min 140.86% 45.02% 239 ppb wash Control - 2-3 min 110 1.72% 40.87% 278 ppb washControl - 15 min wash 110 1.68% 41.02% 231 ppb 1% Cysteine - 15 min 1101.41% 44.02%  67 ppb wash

As shown in this table, immersing potato slices of 0.053 inch thicknessfor 15 minutes in an aqueous solution containing a concentration of oneweight percent of cysteine is sufficient to reduce the acrylamide levelof the final product on the order of 100-200 ppb.

The invention has also been demonstrated by adding cysteine to the corndough (or masa) for tortilla chips. Dissolved L-cysteine was added tocooked corn during the milling process so that cysteine was uniformlydistributed in the masa produced during milling. The addition of 600 ppmof L-cysteine reduced acrylamide from 190 ppb in the control product to75 ppb in the L-cysteine treated product.

Any number of amino acids can be used with the invention disclosedherein, as long as adjustments are made for the collateral effects ofthe additional ingredient(s), such as changes to the color, taste, andtexture of the food. Although all examples shown utilize α-amino acids(where the —NH₂ group is attached to the alpha carbon atom), theapplicants anticipate that other isomers, such as β- or γ-amino acidscan also be used, although β- and γ-amino acids arc not commonly used asfood additives. The preferred embodiment of this invention usescysteine, lysine, and/or glycine. However, other amino acids, such ashistidine, alanine, methionine, glutamic acid, aspartic acid, proline,phenylalanine, valine, and arginine may also be used. Such amino acids,and in particular cysteine, lysine, and glycine, are relativelyinexpensive and commonly used as food additives. These preferred aminoacids can be used alone or in combination in order to reduce the amountof acrylamide in the final food product. Further, the amino acid can beadded to a food product prior to heating by way of either adding thecommercially available amino acid to the starting material of the foodproduct or adding another food ingredient that contains a highconcentration level of the free amino acid. For example, casein containsfree lysine and gelatin contains free glycine. Thus, when Applicantsindicate that an amino acid is added to a food formulation, it will beunderstood that the amino acid may be added as a commercially availableamino acid or as a food having a concentration of the free amino acid(s)that is greater than the naturally occurring level of asparagine in thefood.

The amount of amino acid that should be added to the food in order toreduce the acrylamide levels to an acceptable level can be expressed inseveral ways. In order to be commercially acceptable, the amount ofamino acid added should be enough to reduce the final level ofacrylamide production by at least twenty percent (20%) as compared to aproduct that is not so treated. More preferably, the level of acrylamideproduction should be reduced by an amount in the range of thirty-five toninety-five percent (35-95%). Even more preferably, the level ofacrylamide production should be reduced by an amount in the range offifty to ninety-five percent (50-95%). In a preferred embodiment usingcysteine, it has been determined that the addition of at least 100 ppmcan be effective in reducing acrylamide. However, a preferred range ofcysteine addition is between 100 ppm and 10,000 ppm, with the mostpreferred range in the amount of about 1,000 ppm. In preferredembodiments using other effective amino acids, such as lysine andglycine, a mole ratio of the added amino acid to the reducing sugarpresent in the product of at least 0.1 mole of amino acid to one mole ofreducing sugars (0.1:1) has been found to be effective in reducingacrylamide formation. More preferably the molar ratio of added aminoacid to reducing sugars should be between 0.1:1 and 2:1, with a mostpreferable ratio of about 1:1.

The mechanisms by which the select amino acids reduce the amount ofacrylamide found are not presently known. Possible mechanisms includecompetition for reactant and dilution of the precursor, which willcreate less acrylamide, and a reaction mechanism with acrylamide tobreak it down.” Possible mechanisms include (1) inhibition of Maillardreaction, (2) consumption of glucose and other reducing sugars, and (3)reaction with acrylamide. Cysteine, with a free thiol group, acts as aninhibitor of the Maillard reaction. Since acrylamide is believed to beformed from asparagine by the Maillard reaction, cysteine should reducethe rate of the Maillard reaction and acrylamide formation. Lysine andglycine react rapidly with glucose and other reducing sugars. If glucoseis consumed by lysine and glycine, there will be less glucose to reactwith asparagine to form acrylamide. The amino group of amino acids canreact with the double bond of acrylamide, a Michael addition. The freethiol of cysteine can also react with the double bond of acrylamide.

It should be understood that adverse changes in the characteristics ofthe final product, such as changes in color, taste, and texture, couldbe caused by the addition of an amino acid. These changes in thecharacteristics of the product in accordance with this invention can becompensated by various other means. For example, color characteristicsin potato chips can be adjusted by controlling the amount of sugars inthe starting product. Some flavor characteristics can be changed by theaddition of various flavoring agents to the end product. The physicaltexture of the product can be adjusted by, for example, the addition ofleavening agents or various emulsifiers.

While the invention has been particularly shown and described withreference to several embodiments, it will be understood by those skilledin the art that various other approaches to the reduction of acrylamidein thermally processed foods by use of an amino acid additive may bemade without departing from the spirit and scope of this invention. Forexample, while the process has been disclosed with regard to potato andcorn products, the process can also be used in processing of foodproducts made from barley, wheat, rye, rice, oats, millet, and otherstarch-based grains, as well as other foods containing asparagine and areducing sugar, such as sweet potatoes, onion, and other vegetables.Further, the process has been demonstrated in potato chips and cornchips, but can be used in the processing of many other food products,such as other types of snack chips, cereals, cookies, crackers, hardpretzels, breads and rolls, and the breading for breaded meats. In manyof these foods, the amino acid can be added during the mixing of thedough used to make the product, making the amino acid available duringcooking to provide a reduction in the level of acrylamide. Further, theaddition of an amino acid can be combined with other strategies for thereduction of acrylamide to produce an acceptable acrylamide levelwithout adversely affecting the taste, color, odor, or othercharacteristics of an individual food.

1. A method of preparing corn chips, said method comprising the stepsof: a) preparing a mixture containing ground corn, water, and a freeamino acid in a quantity sufficient to reduce the formation ofacrylamide in said corn chips to a level that is lower than if the freeamino acid had not been added; b) sheeting and cutting said mixture toform chips; and c) thermally processing said chips.
 2. The method ofclaim 1, wherein said free amino acid is chosen from the groupconsisting of cysteine, lysine, glycine, histidine, alanine, methionine,glutamic acid, aspartic acid, proline, phenylalanine, valine, arginine,and mixtures thereof.
 3. The method of claim 1, wherein said thermallyprocessing step c) comprises baking.
 4. The method of claim 1, whereinsaid thermally processing step c) comprises frying.
 5. The method ofclaim 1, wherein, in said adding step a), said food product is soaked ina solution containing said free amino acid.
 6. The method of claim 1,wherein said adding step a) adds an amount of said free amino acid thatis sufficient to reduce said final level of acrylamide in said thermallyprocessed food by at least 20 percent.
 7. The method of claim 1, whereinsaid adding step a) adds an amount of said free amino acid that issufficient to reduce said final level of acrylamide in said thermallyprocessed food by at least 35 percent.
 8. The method of claim 1, whereinsaid adding step a) adds an amount of said free amino acid that issufficient to reduce said final level of acrylamide in said thermallyprocessed food by at least 50 percent.
 9. The method of claim 1, whereinsaid adding step a) adds an amount of said free amino acid that issufficient to reduce said final level of acrylamide in said thermallyprocessed food by at least 65 percent.
 10. The method of claim 1,wherein said mixture at step a) comprises an ingredient comprising saidfree amino acid.
 11. A method of lowering the level of acrylamide in athermally processed food containing free asparagine and simple sugars,said method comprising the steps of: a) adding a free amino acid to afood product, wherein said free amino acid is selected from the groupconsisting of lysine, methionine, glutamic acid, and mixtures thereof,and wherein said ingredient is added in an amount sufficient to reducethe final level of acrylamide in said thermally processed food to alevel that is lower than if the flee amino acid had not been added; andb) thermally processing said food product.
 12. The method of claim 11,wherein said adding step a) adds an amount of said free amino acid thatis sufficient to reduce said final level of acrylamide in said thermallyprocessed food by at least 20 percent.
 13. The method of claim 11,wherein said adding step a) adds an amount of said free amino acid thatis sufficient to reduce said final level of acrylamide in said thermallyprocessed food by at least 35 percent.
 14. The method of claim 11,wherein said adding step a) adds an amount of said free amino acid thatis sufficient to reduce said final level of acrylamide in said thermallyprocessed food by at least 50 percent.
 15. The method of claim 11,wherein said adding step a) adds an amount of said free amino acid thatis sufficient to reduce said final level of acrylamide in said thermallyprocessed food by at least 65 percent.
 16. The method of claim 11,wherein at least 100 parts per million of cysteine is further added inaddition to said free amino acid added in step a).
 17. The method ofclaim 11, wherein about 1,000 parts per million of cysteine is furtheradded in addition to said free amino acid added in step a).
 18. Themethod of claim 11, wherein said adding step a) adds at least 0.1 molesof said amino acid for each mole of reducing sugar in said food product.19. The method of claim 11, wherein said adding step a) adds about 1.0moles of said amino acid for each mole of reducing sugar in said foodproduct.
 20. The method of claim 11, wherein said adding step a) addstip to 2.0 moles of said amino acid for each mole of reducing sugar insaid food product.
 21. The method of claim 11, wherein said free aminoacid added at step a) comprises lysine.
 22. The method of claim 11,wherein said adding step a) adds a commercially available amino acid tosaid food product.
 23. The method of claim 11, wherein said adding stepa) adds a food containing said free amino acid to said food product. 24.The method of claim 11, wherein, in said adding step a), said foodproduct is soaked in a solution containing said free amino acid.
 25. Themethod of claim 11, wherein said free amino acid is mixed with otheringredients to form dough.
 26. The method of claim 11, wherein saidthermal processing in step b) comprises frying said food product. 27.The method of claim 11, wherein said thermal processing in step b)comprises baking said food product.
 28. The method of claim 11, whereinthe adding step a) further comprises adding calcium to said foodproduct.
 29. The method of claim 28, wherein said calcium comprisescalcium chloride.
 30. A method of preparing fabricated potato chips,said method comprising the steps of: a) preparing a dough comprisingpotato flakes, water, and a free amino acid, wherein said amino acid isselected from the group consisting of lysine, methionine, glutamic acid,and mixtures thereof, and wherein said ingredient is added in an amountsufficient to reduce the final level of acrylamide in said fabricatedpotato chips to a level that is lower than if the free amino acid hadnot been added; b) sheeting and cutting said mixture to form cut pieces;and c) thermally processing said cut pieces to form chips.
 31. Themethod of claim 30, wherein said free amino acid comprises lysine. 32.The method of claim 30, wherein said thermally processing step a)comprises baking.
 33. The method of claim 30, wherein said thermallyprocessing step c) comprises frying.
 34. The method of claim 30 whereinsaid dough comprises an ingredient comprising said free amino acid.